This invention relates to novel ester derivatives of prostaglandin F.sub.2.alpha. (hereinafter identified as "PGF.sub.2.alpha. "), 15(S)-15-methyl-PGF.sub.2.alpha., and 15(R)-15-methyl-PGF.sub.2.alpha., including their racemic compounds, and to processes for producing them.
PGF.sub.2.alpha. is represented by the formula: ##STR3## A systematic name for PGF.sub.2.alpha. is 7-{3.alpha.,5.alpha.-dihydroxy-2.beta.-[(3S)-3-hydroxy-trans-1-octenyl]-1. alpha.-cyclopentyl}-cis-5-heptenoic acid. PGF.sub.2.alpha. is known to be useful for a variety of pharmacological and medical purposes, for example, labor induction and abortion in pregnant animals, including humans, menstrual regulation in both pregnant and non-pregnant animals, including humans, treatment of asthma, and the inhibition of blood platelet aggregation. See Bergstrom et al., Pharmacol. Rev. 20, 1 (1968) and references cited therein. As to racemic PGF.sub.2.alpha., see for example W. P. Schneider, Chem. Commun. 304 (1969).
The 15-methyl-PGF.sub.2.alpha. analogs are represented by the formula: ##STR4## wherein M' is ##STR5## following the usual convention wherein broken line attachment of hydroxy to the side chain at carbon 15 indicates the natural or "S" configuration. See for example Nugteren et al., Nature 212, 38 (1966) and Cahn, J. Chem. Ed. 41, 116 (1964). The 15-methyl-PGF.sub.2.alpha. analogs in their optically active and racemic forms are known. See for example U.S. Pat. Nos. 3,728,382 and 3,804,890.
Esters of the above compounds are known, wherein the hydrogen atom of the carboxyl group is replaced by a hydrocarbyl or substituted hydrocarbyl group. Among these are the methyl ester of PGF.sub.2.alpha. (B. Samuelsson, J. Biol. Chem. 238, 3229 (1963)), the phenyl and alkyl-phenyl esters of PGF.sub.2.alpha. (British Spec. No. 1,282,661, Derwent Farmdoc No. 67438R), the .alpha.-naphthyl ester of PGF.sub.2.alpha. (Belgian Pat. No. 775,106, Derwent Farmdoc No. 33705T) and the methyl esters of 15(S)-15-methyl-PGF.sub.2.alpha. and of 15(R)-15-methyl-PGF.sub.2.alpha. (U.S. Patents cited above).